Wednesday, October 31, 2018

Season 13 superfinal, games 41-50

After 50 games Stockfish leads 5-2 with 43 draws.
The draw rate continues to be high at 86%, with half the superfinal over. Komodo and Stockfish both added one win, nothing is over though Stockfish has a promising lead.

Stockfish started game 41 with an eval around 1. It had a space advantage and Komodo's pieces had very little room to move. Stockfish pushed pawns on the king side, the black pieces were in no position to threaten the white king. Evals continued to climb, Stockfish's eval was around 2 at move 19.

Stockfish's king side pawns made contact with Komodo's pawns and slowly opened the king side.The white king was completely exposed yet completely safe from attacks. Komodo's pieces were helpless as Stockfish prepared its attack on the black king.

Komodo tried to exchange pieces but it was too late. The game reached a QRB vs QRN position and Stockfish grabbed two pawns.The game was adjudicated before the white passers advanced.

In game 42 Komodo was up a pawn with a central passer on move 16. Stockfish's bishop pair was very strong and evals fell to 0. In a series of exchanges Stockfish gave a rook for a bishop, the white king was exposed and all the black pieces had clear lines of attack. When the white passer advanced Stockfish ended the game with perpetual check. Another minimatch win for Stockfish.

Stockfish had an eval around 1 from the start of game 43, it was a pawn up on move 14. Evals did not change for a while, then started to increase after the queen side was blocked. The engines exchanged all rooks through an open file, Stockfish's eval was over 2. Only QB vs QB remained and there was a sudden drop in eval, apparently Komodo found a line that Stockfish overlooked. The game reduced to a queen ending, one pawn advantage was not enough for a win since Komodo had too many check attacks. 

Komodo gave a pawn early in game 44, it developed its pieces faster and it forced the black king to move. Stockfish's king side rook was trapped in the corner, while Komodo's knights supported each other while staring directly at the black king.

Komodo gradually increased the pressure on the pawn on d6. Evals started to increase as Komodo doubled rooks on the d file, pinning the pawn, then added a knight and pawn to the attack. Stockfish was still a pawn ahead but evals were over 1 in favor of Komodo.

The tension was released after a series of exchanges in the center, resulting in a QRN vs QRB position with Komodo a pawn up. Komodo continued to exchange pieces reaching a N vs B ending.

Both engines agreed the pawn advantage was enough for a win, the game was adjudicated before the win was played out. Komodo wins its second minimatch.

Stockfish had an eval advantage from the start of game 45, its eval stayed under 1. Komodo had a pawn majority on the queen side, it kept the pawns safe though they were disconnected. Evals dropped to 0 in a series of exchanges that started with a Komodo knight sacrifice on the king side and ended in a BN vs R imbalance. The engines reduced to a BBN vd RB position and the game was adjudicated by the draw rule. In the reverse game 46 evals stayed low. Stockfish had a pawn majority on the queen side and Komodo created an advanced passer in the center. The game reduced to a rook ending, all the passers were captured resulting in a draw.

In game 47 Stockfish pushed pawns on the king side, exposing its king. Evals dropped to 0, Stockfish opened the king side while Komodo controlled an open file in the center. Stockfish sacrificed a bishop and forced a draw with perpetual check. In game 48 both engines castled long. Komodo had a small eval advantage for a long while, many pieces were on the board, both engines avoided exchanges. After queens and rooks were exchanged only BB vs BN remained on move 45. Evals went slowly down to 0 until adjudication.

The engines castled in opposite directions in games 49-50. Stockfish had an eval around 1 from the start of game 49. Stockfish tried to open the king side and was only partially successful, Komodo countered with a central passer. After some shuffling evals dropped to 0, a series of exchanges resulted in a RBN vs RBN position and the game was adjudicated a draw. In game 50 Komodo succeeded in opening the king side, though after the queens were exchanged the black king was not in danger. Evals were low for most of the game, the engines gradually exchanged pieces until reaching a tablebase draw.

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